Radiation-curable composition for optical fiber coating materials

ABSTRACT

Compositions for use in optical fiber coatings and optical fibers and optical fiber arrays using these coatings are disclosed, as are methods for making the same. The compositions comprise a combination of two different radiation curable urethane oligomers, and can further comprise one or more reactive monomers. One of the oligomers has at least three functional groups that can undergo radiation cure, and comprises a lactone modified polyol.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation-in-part of U.S. patentapplication Ser. No. 10/360,176, filed Feb. 6, 2003.

FIELD OF THE INVENTION

[0002] The present invention relates to radiation-curable compositionsuseful as coatings for optical fibers. More specifically, thesecompositions comprise a unique combination of two different radiationcurable urethane oligomers; one or more mono- or polyfunctional reactivemonomers can also be included.

BACKGROUND OF THE INVENTION

[0003] Optical glass fibers have become integral to thetelecommunications industry. While the fibers are exceptionally strong,they are easily flawed such as by exposure to environmental factorsincluding dust and moisture. It is therefore desired to coat the fibersalmost immediately after formation with one or more coating materials.In some cases these fibers have one coating material and in other casestwo or more coatings may be used. For example, the fibers may be coatedwith a soft inner primary coating and a tougher secondary coating; thesecondary coating typically provides a more durable exterior for theoptical fiber. The outermost coating layer is often colored, such as byapplication of an ink layer or through addition of a colorant to thecoating material itself. Color coding of the fibers allows for easieridentification of the individual coated optical glass fibers. This isparticularly relevant in industries where a plurality of fibers areaggregated into a cable. In such applications, the fibers are typicallybonded together in a matrix material. For example, the matrix materialcan encase the optical fibers or can edge bond the optical fiberstogether.

[0004] It is generally desired that the matrix material used in opticalfiber assemblies will provide both the desired level of “toughness”while still allowing for flexibility. The physical properties of thematrix components, such as the polymers, can be related to theperformance of the matrix material. For example, a suitable matrixmaterial will typically have a glass transition temperature (“Tg”) highenough to allow acceptable heat strip for peelable optical fiber ribbonand to provide resistance to environmental attacks such as by moistureand/or chemicals. The matrix material should also have an elongationsufficient to render the ribbon robust in various handling operations,such as in heat strip operations. Since the matrix material will mosttypically be in direct contact with the outermost coating on the fibers,it is also desirable that the matrix material release from the fiberswhen necessary, such as when repairing or branching is needed. Theability to access individual fibers in a ribbon matrix without damagingthe fiber or any coating or identification thereon is an importantfeature. The ability to release, however, must be countered against theability to adhere to the fibers during use. The matrix material shouldalso have high resistance to thermal, oxidative and hydrolyticdegradation. The ability to cure rapidly, such as upon exposure to UVradiation, can also be an important feature. Thus, there are a number ofdesirable characteristics for a matrix material, and it is often thecase with compositions known in the art that improvement of onecharacteristic results in the sacrifice of another.

[0005] Similarly, secondary coatings used with optical fibers have anumber of desirable characteristics. For example, such coatings shouldfunction as a hard, tough protective outer layer, preventing damage tothe glass fiber during processing and use. A secondary coating shouldundergo minimal changes in physical properties upon exposure to organicsolvents and moisture. A secondary coating should also have acoefficient of friction that facilitates winding and unwinding of thefibers on spools and allows the fibers to slide easily along each otherin a cable structure, thus relieving stress, yet also allows the fibersto stay aligned on the spool.

SUMMARY OF THE INVENTION

[0006] The present invention provides a curable composition that findsparticular application as an optical fiber coating material and isespecially suitable as a matrix material and/or a secondary coating. Thecomposition comprises two different radiation curable urethanecomponents. The first of these components imparts to the composition ahigh Tg, that is, a Tg equal to or greater than about 50° C. The secondof these components imparts a high elongation to the composition, thatis, an elongation equal to or greater than about 15 percent. Thecomposition can further comprise one or more reactive monomers; thesemonomers can be monofunctional, polyfunctional or combinations thereof.Various additives can also be included, such as photoinitiators, thermalinitiators, releasing agents, anti-oxidants, stabilizers, UV absorbers,adhesion promoters and the like.

[0007] The present compositions therefore combine the characteristics ofhigh Tg and high elongation. These properties are particularly desirablein matrix and secondary fiber coatings. Other desired characteristics ofoptical fiber matrix materials and fiber coatings, such as good curingspeed and high resistance to various environmental factors, are alsoprovided by the present compositions.

[0008] The present invention is further directed to optical fiber ribbonarrays containing secondary coatings and/or matrices prepared from thepresent compositions, and to processes for preparing these arrays.

DETAILED DESCRIPTION OF THE INVENTION

[0009] The present invention is directed to a composition comprising acombination of two different radiation curable urethane components. A“radiation curable urethane component” is a compound having urethanelinkages and at least one functional group that can be cured by exposureto radiation. The first of these components generally imparts a high Tgto the compositions of the invention, and comprises at least threeradiation curable functionalities. The second of these componentsgenerally imparts a high elongation to the present compositions. Thesecond component is generally different from the first and may, but neednot, have at least three radiation curable functionalities; in certainembodiments it has at least one such functionality. The presentcompositions can also include one or more mono- or poly-functionalreactive monomers that can also influence the properties of the coatingcompositions. Additives standard in the art, such as photoinitiators,thermal initiators, releasing agents, anti-oxidants, UV absorbers,stabilizers and the like can also optionally be added.

[0010] The first radiation curable urethane generally imparts a Tg tothe final composition of equal to or greater than about 50° C.Particularly suitable for matrix coatings are those that impart a Tg ofequal to or greater than about 85° C.; particularly suitable forsecondary coatings are those that impart a Tg of equal to or greaterthan about 55° C. The Tg of the composition can be measured using adynamic mechanical analyzer following methods standard in the art, suchas those described in the examples below. As used herein, “Tg” isdefined as the temperature at the peak of Tan δ during a dynamic thermomechanical test. It should be noted that “high Tg” refers to the Tg ofthe final composition and not the Tg of the radiation curable urethaneitself.

[0011] The high Tg imparting radiation curable urethane can be formed bymeans standard in the art, such as through the reaction of a curablefunctionality-terminating aromatic-containing polyol oligomer, apolyisocyanate and an endcapping monomer. A particularly suitablestarting material is one where the polyol oligomer is adiphenylmethane-containing polyol oligomer. A“diphenylmethane-containing polyol oligomer” refers to a compoundcontaining at least one diphenylmethane moiety and comprising twoterminating curable functionalities and at least two hydroxylfunctionalities. The diphenylmethane-containing polyol generallycomprises from 1 to 4 diphenylmethane groups and can be depicted byformula I:

[0012] In formula I, R₁, R₁′, R₁″, and R₁′″ are the same or differentand are selected from hydrogen or a linear or branched lower alkyl grouphaving 1 to 16 carbon atoms; R₂ and R₂′ are the same or different andare selected from linear or branched alkyl groups having 2 to 8 carbonatoms; R₃ and R₃′ are the same or different and comprise reactivemoieties selected from acrylic, methacrylic, vinylic, allylic, styrenic,acrylamide, norbornenyl, acetylenic, epoxy, mercapto, amino, itanoic andcrotonic moieties; a and c are the same or different and are from 0 to20; and b is from 0 to 3. The “R₁” structures are typically hydrogen,methyl, ethyl, propyl, butyl and the like. In a particularly suitableembodiment, R₃ and R₃′ are acrylic ester structures, b is 0 and a and care 0 to 6. Even more suitable is an embodiment wherein all of the “R₁”structures are methyl and a, b, and c are all 0. Typically, thesepolyols are derived from diacrylated bisphenol diglycidyl ethers ortheir alkoxylated derivatives, i.e. compounds where there are alkoxylchains between the bisphenol structure and the glycidyl structure. In aparticularly suitable embodiment, the bisphenols used in producing thesepolyols are bisphenol A. Examples of such polyols include the so-calledepoxy acrylate oligomers from Sartomer Company (Exton, Pa.) known asCN-104 and CN-120 and UCB in their EBECRYL line of products. When adiphenylmethane-containing polyol is used, it will be understood thatthe oligomer is not wholly aliphatic.

[0013] In one embodiment, the polyol oligomer has been modified with alactone. In a specific embodiment, the diphenylmethane-containing polyololigomer as described above has been modified with a lactone. Typically,the diphenylmethane-containing polyol oligomer contains secondaryhydroxyl groups that are relatively hindered and unreactive. By reactingthe secondary hydroxyl groups with a cyclic lactone, the secondaryhydroxyl groups are transformed into primary hydroxyl groups. Any cycliclactone can be used according to the present invention; particularlysuitable are ε-caprolactone and its derivatives. Polyol oligomers thathave been reacted with a lactone are referred to herein as “modifiedwith a lactone”, “lactone modified” or similar terms. The primaryhydroxyl groups derived from this reaction can then be reacted with anisocyanate group. It will be appreciated that transforming a secondaryhydroxyl group into a primary hydroxyl group facilitates its reactionwith an isocyanate group. In addition to the favorable impact on thereaction, modification with the cyclic lactone also results in a moreflexible oligomer having better or higher elongation. Surprisingly,better elongation is achieved this way without impacting the Tg of theoligomer or composition.

[0014] The polyisocyanate component can be either aromatic or aliphatic.Aliphatic polyisocyanates of from 4 to 20 carbon atoms may be employed.Suitable saturated aliphatic polyisocyanates include but are not limitedto isophorone diisocyanate, methylenebis(4-cyclohexyl isocyanate),hydrogenated diphenylmethane diisocyanate, hydrogenated xylylenediisocyanate, 1,4-cyclohexyl diisocyanate, 1,3-cyclohexyl diisocyanate.Isophorone diisocyanate and methylenebis(4-cyclohexyl isocyanate) areparticularly suitable. Suitable aromatic polyisocyanates include2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 1,3-xylylenediisocyanate, 1,4-xylylene diisocyanate, 1,5-naphthalene diisocyanate,m-phenylene diisocyanate, p-phenylene diisocyanate,3,3′-dimethyl-4,4′-diphenylmethane diisocyanate, 4,4′-diphenylmethanediisocyanate, 3,3′-dimethylphenylene diisocyanate, 4,4′-biphenylenediisocyanate, and mixtures thereof.

[0015] The endcapping monomer may be one that is capable of providing atleast one radiation curable functionality, which, for example, may beacrylic, methylacrylic, vinylic, allylic, styrenic, acrylamide,norbornenyl, acetylenic, epoxy, mercapto, amino, itanoic, and crotonicmoieties. The radiation-curable functionality typically used isethylenic unsaturation, which can be polymerized through radicalpolymerization or cationic polymerization. Specific examples of suitableethylenic unsaturation are groups containing (meth)acrylate, styrene,vinylether, vinyl ester, N-substituted acrylamide, N-vinyl amide,maleate esters, and fumarate esters. “(Meth)acrylate” refers to bothmethacrylate and acrylate. Acrylate functionality is particularlysuitable. Endcapping monomers that provide acrylate or methacrylatetermini are particularly suitable and include but are not limited tohydroxyalkyl(meth)acrylates such as hydroxyethyl(meth)acrylate,hydroxypropyl(meth)acrylate, hydroxybutyl(meth)acrylate,2-hydroxy-3-phenyloxypropyl (meth)acrylate, 1,4-butanediolmono(meth)acrylate, 4-hydroxycyclohexyl (meth)acrylate, 1,6-hexanediolmono(meth)acrylate, neopentyl glycol mono(meth )acrylate,trimethylolpropane di(meth)acrylate, trimethylolethane di(meth)acrylate,pentaerythritol tri(meth)acrylate, dipentaerythritolpenta(meth)acrylate, and the like. A particularly suitable endcappingmonomer is hydroxyethyl(meth)acrylate. 4-hydroxybutyl vinyl ether is aparticularly suitable endcapping group for introducing vinyl ethertermini.

[0016] The molar ratio of the polyol, polyisocyanate and endcappingmonomer used in preparing the high Tg imparting component in oneembodiment is typically about 1:2-3:1-2. A particularly suitable ratiois 1:2.5:1.5. A high Tg urethane acrylate based on the polyol of generalformula I will have a structure as depicted in formula II:

[0017] All the hydroxyl groups from formula I are shown in formula II asan “R₄” structure (R₄, R₄′, and R₄″). R₄, R₄′, and R₄″ can be the sameor different and are selected from hydroxy groups and the reactivegroups containing curable functionalities as defined above for R₃ andR₃′ and at least one of the “R₄” structures contains any of the reactivegroups as defined above for R₃ and R₃′. It will be understood that onlyone of the hydroxyl groups shown in formula I needs to be functionalizedto be within the present invention; such a molecule would contain threeradiation-curable functionalities. The remaining “R₄” structures, if notfurther functionalized, would just be hydroxyl groups.

[0018] It is evident that one skilled in the art can devise othermethods to synthesize the urethane compounds having structures as shownin formula II. For example, such a product can be derived from asuitable alkoxylated bisphenol A diol, a diisocyanate, and a suitableendcapping monomer having more than one radiation curable moiety.

[0019] The high Tg imparting urethane component is typically present inthe compositions of the invention in amounts from 20 to 80 weightpercent, such as from 30 to 70 weight percent, with weight percent beingbased on the total weight of the two urethane oligomers, or from 10 to40 weight percent, with weight percent being based on the total weightof the composition.

[0020] The second component of the present composition is a radiationcurable urethane oligomer that imparts high elongation to the presentcompositions. By “high elongation” is meant an elongation at break ofequal to or greater than about 15 percent. The elongation will typicallybe less than 100 percent. In one embodiment, the coating is a matrixcoating having an elongation of 35 to 65 percent and in anotherembodiment the coating is a secondary coating having an elongation of 15to 25 percent.

[0021] Whether a particular radiation curable urethane polymer imparts ahigh elongation to a composition can be determined by one skilled in theart using standard methods. More specifically, the radiation curableurethane can be prepared and added into the present compositions, whichcan then be tested for elongation on an Instron according to ASTM D-882using 5 mil films. It should be noted that “high elongation” refers tothe elongation of the final composition and not the elongation of theradiation curable urethane itself.

[0022] The high elongation imparting component can be prepared byreacting a polyol, a polyisocyanate and an endcapping monomer. Morespecifically, the high elongation imparting urethane component of thepresent compositions is the reaction product of an aliphatic or aromaticpolyol, an aliphatic or aromatic polyisocyanate, and an endcappingmonomer capable of supplying a reactive terminus. The polyol used in thereaction will typically be based on a diol having an Mn of at leastabout 2000 daltons. This includes polyether polyols such as polyolsobtained by ring-opening polymerization or copolymerization of at leastone type of compound selected from ethylene oxide, propylene oxide,butylene oxide, tetrahydrofuran, 2-methyl-tetrahydrofuran,3-methyl-tetrahydrofuran, oxetane, and substituted oxetane. Othersuitable polyols include propylene glycol and polypropylene glycol.Mixtures of all of these polyols can also be used. Examples of desirablepolyol compounds are polytetramethylene glycol with an Mn of at least2000 daltons. Particularly suitable polyols are polyTHF 2000 and polyTHF2900 from BASF Corporation as well as TERATHANE 2000 and TERATHANE 2900from DuPont. Other examples of desirable polyol compounds arepolypropylene glycols with a number average molecular weight of at least2000 such as PPG 2025 from Bayer or PLURACOL 4000 from BASF Corporation.Aromatic polyols can also be used here provided their Mn is at least2000. Smaller polyols with more than two hydroxyl groups are also oftenused in addition to these relatively high molecular weight diols. Suchpolyols include 1,1,1-trimethylolpropane and its dimer, pentaerythritoland its dimer, glycerine and ribose, with 1,1,1-trimethylolpropane beingparticularly suitable.

[0023] Many of the aliphatic and aromatic polyisocyanates listed abovefor the high Tg imparting component can also be used here.Tetramethylxylylene diisocyanate (TMXDI) is especially suitable.Additional suitable aliphatic polyisocyanates include 1,4-tetramethylenediisocyanate, 1,5-pentamethylene diisocyanate, 1,6-hexamethylenediisocyanate, 1,7-heptamethylene diisocyanate, 1,8-octamethylenediisocyanate, 1,9-nonamethylene diisocyanate, 1,10-decamethylenediisocyanate, and mixtures thereof. It will be appreciated that many ofthe aliphatic isocyanates listed here are more suited to the highelongation imparting component than the high Tg imparting component;that is because these isocyanates are very flexible and give low Tgmaterials.

[0024] The endcapping monomer is also described above for the high Tgimparting component; hydroxy alkyl acrylates are again particularlysuitable.

[0025] The molar ratio of polyol, polyisocyanate and endcapping monomerused in preparing the high elongation imparting component is typically0.8-3.0:1.0-4.0:1; a particularly suitable ratio is 1.0-2.2:1.5-3.0:1.

[0026] A particularly suitable high elongation imparting componentcombines polytetramethylene glycol having an Mn of 2000 withtrimethylolpropane, TMXDI, and hydroxyethyl acrylate in a molar ratio of2.1:2.8:1. TERATHANE 2000 is a polytetramethylene glycol having an Mn of2000. It will be appreciated that this molecule contains aromaticity andis therefore not wholly aliphatic. In one embodiment, both the high Tgand high elongation imparting components have aromatic moieties and thusneither are wholly aliphatic.

[0027] The high elongation imparting radiation curable urethane istypically present in the compositions of the invention in an amount fromabout 20 to 70 weight percent, such as from 30 to 60 weight percent,with weight percent being based on the total weight of the urethanecomponents, or from 10 to 40 weight percent, with weight percent beingbased on the total weight of the composition. In one embodiment, theamount of high elongation imparting component is less than 30 weightpercent and in another embodiment is less than 20 weight percent of thetotal weight of the composition. The ratio of high Tg impartingradiation curable urethane to high elongation imparting radiationcurable urethane typically ranges from about 1:3 to about 3:1.

[0028] In one embodiment, neither of the radiation curable urethaneoligomers contain an isocyanurate structure. In another embodiment theycontain no silicone-modified moieties, aliphatic diisocyanate residuesor propoxylated acrylates, and in yet another embodiment, neither of theoligomers has the structure described as the second oligomer of U.S.Pat. No. 5,837,750, which is hereby incorporated by reference.

[0029] Both of the radiation curable urethane components of the presentcompositions can be prepared using methods standard in the art. Thereare generally two protocols for making the radiation curable urethaneoligomers described herein. One protocol involves reacting theisocyanate component with the polyol first and then reacting theresulting product with the endcapping monomer. It is particularlysuitable to synthesize the high Tg imparting oligomer using thisprotocol. The other protocol involves reacting the isocyanate componentwith the endcapping monomer followed by reaction with the polyol. It isparticularly suitable to prepare the high elongation imparting oligomerusing this protocol. The “polyol”, in the case of the first radiationcurable urethane, refers to the aromatic-containing polyol oligomer.Suitable catalysts can be used to increase the reaction rate between thehydroxyl group and the polyisocyanate; such catalysts are known in theart and include, for example, dibutyltindilaurate, dibutyltinoxide,dibutyl tin di-2-hexoate, stannous oleate, stannous octoate, lead,octoate, ferrous acetoacetate, and amines such as triethyleneamine,diethylmethylamine, triethylenediamine, dimethylethylamine, morpholine,N-ethyl morpholine, piperazine, N,N-dimethyl benzylamine, N,N-dimethyllauralamine and mixtures thereof.

[0030] The composition of the present invention can also be preparedusing methods standard in the art. For example, the two urethaneoligomers can be prepared separately and blended or one oligomer can bemade in the presence of the other, such as sequentially.

[0031] It will be appreciated that the high elongation impartingradiation curable urethane component imparts elongation properties tothe present compositions. It is therefore possible to achieve acomposition having suitable elongation without the use of various thiolelongation promoters, such as the mercapto or sulfide elongationpromoters described in U.S. Pat. No. 6,265,476.

[0032] The present compositions can further comprise one or more mono-or polyfunctional reactive monomers. These monomers can perform numerousfunctions in the present compositions; for example, the reactivemonomer(s) can be used to adjust the viscosity of the coatingcompositions or to increase the crosslinking density of thecompositions. The monomers are reactive, which means they contain atleast one functional group capable of polymerization under radiationcurable conditions.

[0033] The monomers can be mono-, or polyfunctional. A particularlysuitable combination is one in which two monofunctional monomers arecombined with one polyfunctional monomer, such as a tri- ortetra-functional mix. A particularly suitable combination within thisembodiment is one that includes isobornyl acrylate, N-vinylpyrrolidone(“NVP”) and dipentaerythritol pentaacrylate. In this combination, theisobornyl acrylate can be added to the composition to lower theviscosity and contribute to Tg; NVP can be added to contribute to thehigh Tg, a fast cure, and the reduced viscosity of the composition; anddipentaerythritol pentaacrylate can be added to improve the equilibriummodulus by increasing the crosslinking density. Suitable monomers may bestraight or branched chain alkyl, cyclic or partially aromatic monomers,and can comprise, for example, a monomer or monomers having an acrylateor vinyl ether functionality and a C₄-C₂₀ alkyl or polyether moiety.Examples of such reactive monomers include hexyl acrylate,2-ethylhexylacrylate, isobornylacrylate, decylacrylate, laurylacrylate,stearylacrylate, ethoxyethoxy-ethylacrylate, laurylvinylether,2-ethylhexylvinyl ether, N-vinyl formamide, isodecyl acrylate, isooctylacrylate, vinylcaprolactam, N-vinylpyrrolidone, acrylamide, nonylphenolacrylate and the like. In one embodiment, none of the monomers aretransesterified.

[0034] Another suitable type of reactive monomer is a compoundcomprising an aromatic group. Examples include, but are not limited to,ethyleneglycolphenyletheracrylate,polyethyleneglycolphenyletheracrylate,polypropyleneglycolphenyletheracrylate, phenoxyethylacrylate, andalkyl-substituted phenyl derivatives of the above monomers, such aspolyethyleneglycolnonylphenyletheracrylate.

[0035] Further examples of suitable monomers include C₂-C₁₈hydrocarbondioldiacrylates, C₄-C₁₈ hydrocarbondivinylethers, C₃-C₁₈hydrocarbontrioltriacrylates, the polyether analogs thereof, and thelike, such as 1,6-hexanedioldiacrylate, trimethylolpropanetriacrylate,hexanedioldivinylether, triethyleneglycol diacrylate, and alkoxylatedbisphenol A diacrylate. Typically, the reactive monomers will be addedin an amount ranging between about 25 and 75 weight percent of the totalcomposition, such as 30 and 65 weight percent. If more than one reactivemonomer is present, the amounts of monomers are added together todetermine the amount of this component in the present compositions. Oneembodiment of the present invention specifically excludes compositionswherein one of the monomers is that taught in U.S. Pat. No. 5,998,497when a polyether urethane acrylate and photoinitiator are also present;also, the monomers used in the present composition do not have to bespecially purified as in U.S. Pat. No. 6,323,255.

[0036] When there are three or more cyclic rings in 20 to 85 weightpercent of the radiation curable urethane components, and there is alsoa polymerizable mono-functional vinyl monomer having a Tg greater thanabout 50° C., the urethane bonds are present in the composition at aconcentration of less than 2.0×10⁻³ mol per gram.

[0037] It is a feature of the present invention that the compositionsdisclosed herein can be cured by free radical cure. Those skilled in theart will understand that free radical cure includes the steps ofinitiation, propagation, chain transfer and termination. When cationiccurable functional groups are included in the composition, they can alsobe cured by cationic polymerization processes. Cure can be provoked bythe use of actinic light, electron beam or heat depending on theapplication requirements; suitable initiators may also be included toeffect initiation.

[0038] When radiation cure is desired, the present compositions mayfurther comprise at least one photoinitiator. Conventionalphotoinitiators can be used, including benzophenones, acetophenonederivatives, such as alpha-hydroxyalkylphenylketones, benzoin alkylethers and benzyl ketals, monoacylphosphine oxides, and bisacylphosphineoxides. The conventional photoactive onium salts can be used to effectcationic cure. Particularly suitable free radical photoinitiators arecombinations of an acetophenone derivative and a bisacylphosphine oxide,although in one embodiment, the bisacrylphosphine oxides described inU.S. Pat. No. 6,359,025 are specifically excluded.

[0039] When the liquid curable resin composition of the presentinvention is to be heat cured, a thermal polymerization initiator suchas a peroxide or an azo compound can be used. Specific examples includebenzoyl peroxide, t-butyl oxybenzoate and azobisisobutyronitrile.

[0040] The amount of photoinitiator or thermal inhibitor in the presentcompositions will typically range from about 0 to 15 weight percent,such as from about 1 to 8 weight percent, with weight percent beingbased on the total weight of the composition.

[0041] The present compositions can also optionally comprise additivesstandardly known in the art. These additives typically comprise lessthan about 15 weight percent of the present compositions. For example, arelease agent can be added. Examples include γ-aminopropyltriethoxysilane, γ-mercaptopropyl trimethoxysilane, andpolydimethylsiloxane derivatives. Typically, the release agent or agentswill be present in an amount of between about 2 and 3 weight percent. Inone embodiment, a portion of the release agent is particulate, and wouldbe in particulate form even after the present compositions are cured.

[0042] To improve shelf life or storage stability of the compositionprior to cure, as well as to increase thermal and oxidative stability ofthe cured compositions, one or more stabilizers or anti-oxidants can beincluded in the composition.

[0043] Examples of suitable stabilizers include tertiary amines such asdiethylethanolamine and trihexylamine; hindered amines; organicphosphites; hindered phenols; mixtures thereof; and the like. Someparticular examples of antioxidants that can be used include propionatessuch as octadecyl-3-(3′,5′-di-tert-butyl-4′-hydroxyphenyl) propionateand hydrocinnamates such as thiodiethylenebis(3,5-di-tert-butyl-4-hydroxy) hydrocinnamate and tetrakis [methylene(3,5-di-tert-butyl-4-hydroxyhydrocinnamate)] methane. Suitablecommercially available antioxidants include IRGANOX 1010, 1035, 1076,and 1222, manufactured by Ciba Specialty Chemicals Corporation.

[0044] UV absorption agents can also be included including thosecommercially available from Ciba Geigy as TINUVIN P234, 320, 326, 327,328, 329, and 213.

[0045] Still other additives or components that may appear in the finalcoating include pigments, lubricants, wetting agents, adhesion promotersand leveling agents. These additives may be present in an effectiveamount that is usual for the additive when used in optical fibercoatings or protective materials. The person skilled in the art candetermine the additives and amounts that are appropriate for a givenuse.

[0046] The viscosity of the coating composition will typically bebetween about 1000 and 10,000 centipoises (cps) as measured using aBrookfield cone and plate viscometer No. 52 spindle at 5 rpm and 25° C.;a viscosity of between 4000 and 8000 cps is particularly suitable foroptical ribbon matrix and secondary coating applications. Viscosity canbe adjusted by any means known in the art.

[0047] The present compositions can be formulated using techniques andmethods that are standard in the art.

[0048] In addition to high Tg and high elongation, the compositions ofthe present invention have numerous additional characteristics thatrender them suitable for use as optical ribbon coating materials. Forexample, the present compositions will typically have an equilibriummodulus after cure of greater than about 1 MPa and as high as 60 MPa ormore. For matrix coatings, an equilibrium modulus of 1 to 20 isparticularly suitable and for secondary coatings 20 to 60 isparticularly suitable. Equilibrium modulus can be measured using adynamic mechanical analyzer. It has been determined that the use of aradiation curable oligomer comprising three or four radiation curablefunctionalities imparts a higher equilibrium modulus to the finalcomposition than does a radiation curable oligomer comprising only tworadiation curable functionalities. Because there are more functionalgroups on the present oligomers, there is a higher crosslink density andhence a higher equilibrium modulus. The higher the crosslink density the“harder” the coating and the harder it will be for water, oil and thelike to penetrate the coating. Thus, the present compositions areparticularly suitable for applications in which penetration of water,oil, etc. is not desired; in contrast, a difunctional oligomer may notprovide this desired characteristic.

[0049] The Youngs modulus of the present compositions, when cured, istypically greater than about 400 MPa and is typically from 500 to 1200MPa. Youngs modulus is also derived from dynamic mechanical analysis.

[0050] The Secant modulus of the present compositions, when cured, istypically greater than about 300 MPa and is typically from 300 to 1000MPa. Secant modulus is measured using an Instron according to ASTMD-882.

[0051] The Tensile stress at break of the present compositions, whencured, is typically greater than about 22 MPa and is typically between25 and 50 MPa. Tensile stress is measured at 25° C. using an Instronaccording to ASTM D-882.

[0052] One embodiment of the present invention includes compositionsthat specifically exclude unsaturated substituted siloxane adhesionpromoters and/or the adhesion promoters described in U.S. Pat. Nos.5,977,202; 6,316,516; and 6,355,751, all of which are incorporated byreference herein.. In other embodiments, the present compositions do notinclude a phospholipid, nor do they include a chromaphoric indicator.

[0053] The present invention is further directed to an opticalfiber-bonded ribbon array wherein one or more of the coatings are of thepresent invention and method for making such an array. The arraygenerally comprises a plurality of optical fibers that can be coatedwith any coatings standardly used in the art for this purpose, such asthose that are radiation cured, or the present compositions. Anystandard optical fiber can be used according to the invention, such asthose having a glass core and a glass cladding layer. For example, thecore may comprise silica doped with oxides of germanium or phosphorusand the cladding can be a pure or doped silicate, such as afluorosilicate. The fibers may alternatively comprise a polymer cladsilica glass core, such as an organosiloxane polymer cladding. Thecoated fibers are then secured in the desired configuration, such as ina parallel and planar or other prescribed arrangement, and are embeddedin the composition of the present invention. For example, the fibers canbe arranged in the desired manner, the liquid matrix can be applied tothe fibers, and the matrix composition can be cured. The matrixcomposition, when cured, adheres to the fibers during use, but can bestripped therefrom without substantially damaging the integrity of thecoated optical fibers, including any ink layer that has been depositedthereon. Specific embodiments of the present invention include thosewherein the second coating layer on the fiber, the matrix coating layer,or both are comprised of the composition of the present invention. Whenboth the secondary and matrix coatings are within the present invention,they can be the same or different embodiments. The primary coatingunderlying the secondary coating can be any primary coating known in theart, which coatings are widely commercially available.

[0054] As used herein, unless otherwise expressly specified all numberssuch as those expressing values, ranges, amounts or percentages may beread as if prefaced by the word “about”, even if the term does notexpressly appear. Any numerical range recited herein is intended toinclude all sub-ranges subsumed therein. Plural encompasses singular andvice versa. Also, as-used herein, the term “polymer” is meant to referto oligomers and both homopolymers and copolymers. The prefix “poly” asused herein refers to two or more.

EXAMPLES

[0055] The following examples are intended to illustrate the invention,and should not be construed as limiting the invention in any way.“Parts” refers to parts by weight.

Example 1 Preparation of High Tg Imparting Oligomer (1)

[0056] Into a two-liter, four-necked reaction kettle equipped with athermometer, a mechanical stirrer and a condenser were charged 242.0parts of CN-120 (an epoxy diacrylate from Sartomer), 1.4 parts of2,6-di-t-butyl-4-methylphenol, 0.5 parts of dibutyltindilaurate, 0.2parts of phenothiazine, and 219.2 phenoxyethylacrylate. After themixture was heated to 55° C., 277.5 parts of isophorone diisocyanate wasadded while maintaining the reaction temperature at 80° C. or below. Themixture was subsequently held at 85° C. for two hours. A sample wastaken for isocyanate (“NCO”) equivalent weight measurement to confirmthe completeness of the reaction. After all the hydroxyl functionalitywas consumed according to the NCO equivalent measurement result, 354.6parts of hydroxyethyl acrylate and 0.5 parts of dibutyltindilaurate wereadded to the reactor while controlling the temperature at around 80° C.The mixture was held at 80° C. until it was significantly free ofisocyanate functionality as revealed by NCO equivalent weightmeasurements. The NCO equivalent weight measurements were performed,which were accomplished by reacting any residual NCO functionality withan excess amount dibutylamine. The amount of amine consumed (if any) canbe then calculated from titrating the amine with a standard acidicsolution.

Example 2 Preparation of High Tg Imparting Oligomer (2)

[0057] Into a two-liter, four-necked reaction kettle equipped with athermometer, a mechanical stirrer and a condenser were charged 242.0parts of CN-104 (an epoxy diacylate from Sartomer), 1.4 parts of2,6-di-t-butyl-4-methylphenol, 0.5 parts of dibutyltindilaurate, 0.2parts of phenothiazine, and 219.2 phenoxyethylacrylate. After themixture was heated to 55° C., 277.5 parts of isophorone diisocyanate wasadded while maintaining the reaction temperature at 80° C. or below. Themixture was subsequently held at 85° C. for two hours. A sample wastaken for isocyanate (“NCO”) equivalent weight measurement to confirmthe completeness of the reaction. After all the hydroxyl functionalitywas consumed according to the NCO equivalent measurement result, 354.6parts of hydroxyethyl acrylate and 0.5 parts of dibutyltindilaurate wereadded to the reactor while controlling the temperature at around 80° C.The mixture was held at 80° C. until it was significantly free ofisocyanate functionality as revealed by NCO equivalent weightmeasurements.

Example 3 Preparation of High Elongation Imparting Oligomer (3)

[0058] Into a two-liter, four-necked reaction kettle equipped with athermometer, a mechanical stirrer and a condenser were charged 190.4parts of meta-tetramethylene diisocyanate, 327.6 parts of isobornylacrylate, 9.6 parts of trimethylolpropane, 0.5 parts ofdibutyltindilaurate, 1.4 parts of 2,6-di-t-butyl-4-methylphenol and 0.2parts of phenothiazine. The mixture was heated up and held at 80° C.until the NCO equivalent weight was within the theoretical value. Themixture was then cooled to 35° C. and 32.4 parts of hydroxyethylacrylate was added to the reactor. Cooling was applied to the reactorduring the addition as necessary to control the reaction temperature tobelow 40° C. The mixture was then held at 38° C. for two hours. A samplewas taken for isocyanate equivalent weight measurement to confirm thecompleteness of the reaction. Thereafter, 1053.4 parts of PolyTHF2000and 0.5 parts of dibutyltindilaurate were added to the reactor whilecontrolling the temperature to around 65° C. The mixture was then heldat 65° C. until it was significantly free of isocyanate functionality asrevealed by NCO equivalent weight measurements.

Example 4 Formulation (1)

[0059] Into a three liter, four-necked reaction kettle equipped with athermometer, a mechanical stirrer, and a condenser were charged 673.6parts of N-vinyl-2-pyrrolidone (ISP), 164.2 parts ofphenoxyethylacrylate (Sartomer), 126.6 parts of isobornyl acrylate(Sartomer), 286.4 parts of dipentaerythritol pentaacrylate (Sartomer),1005.7 parts of oligomer (1) as synthesized in Example 1 above, and768.2 parts of oligomer (3) as synthesized in Example 3 above. Themixture was heated to 66° C. The mixture was stirred at 66° C. until itbecame clear; 119.0 parts of DAROCUR 4265 (Ciba Additives) were thenadded. Afterwards, the mixture was stirred at 66° C. for 30 minutes. Theformulation had a viscosity of 4423 cps when measured with a Brookfieldviscometer at 25° C.

[0060] A five mil coating of this composition was applied to a flat ofglass plate using a Bird applicator and cured at 1 J/cm2 under a D-lampin a nitrogen atmosphere. The resulting free film gave a tensile stressat break of 46 MPa and an elongation of 43 percent when tested accordingto ASTM D-882. Dynamic mechanical analysis carried out at a frequency of1 Hz, speed of 2° C. per minute from −50° C. to 180° C. on the free filmgave a Tg of 126° C. and an equilibrium modulus of 12.9 MPa.

Formulation (2)

[0061] Into a three liter, four-necked reaction kettle equipped with athermometer, a mechanical stirrer, and a condenser were charged 673.6parts of N-vinyl-2-pyrrolidone (ISP), 164.2 parts ofphenoxyethylacrylate (Sartomer), 126.6 parts of isobornyl acrylate(Sartomer), 286.4 parts of dipentaerythritol pentoacrylate (Sartomer),1005.7 parts of oligomer (2) as synthesized in Example 2 above, and768.2 parts of oligomer (3) as synthesized in Example 3 above. Themixture was heated to 66° C. The mixture was stirred at 66° C. until itbecame clear; 119.0 parts of DAROCUR 4265 were then added. Afterwards,the mixture was stirred at 66° C. for 30 minutes. The formulation had aviscosity of 3814 cps when measured with a Brookfield viscometer at 25°C.

[0062] A five mil coating of this composition was applied to a flat ofglass plate using a Bird applicator and cured at 1 J/cm² under a D-lampin a nitrogen atmosphere. The resulting free film gave a tensile stressat break of 47 MPa and an elongation of 45 percent when tested accordingto ASTM D-882. Dynamic mechanical analysis carried out at a frequency of1 Hz, speed of 2° C. per minute from −50° C. to 180° C. on the free filmgave a Tg of 140° C. and an equilibrium modulus of 16.5 MPa.

Example 5 Preparation of High Tg Imparting Oligomer (4)

[0063] Into a two-liter, four-necked reaction kettle equipped with athermometer, a mechanical stirrer and a condenser were charged 242.00parts of CN-104 (a bisphenol A epoxy based di-acrylate from SARTOMER),1.43 parts of 2,6-di-t-butyl-4-methylphenol, 0.50 parts of dibutyltindilaurate, 0.20 parts of phenothiazine, and 219.20 parts of phenoxyethylacrylate. After the mixture was heated to 55° C., 277.50 parts ofisophorone diisocyanate were charged to the reactor. The mixture washeated to 65° C. and held at that temperature for two hours. A samplewas taken for isocyanate (“NCO”) equivalent weight measurement toconfirm the completeness of the reaction. Thereafter, a mixture of174.00 parts of hydroxyethyl acrylate, 180.61 parts of phenoxyethylacrylate, and 0.50 parts of dibutyltindilaurate were added dropwise tothe reactor while controlling the temperature at around 80° C. Themixture was held at 80° C. until it was significantly free of isocyanatefunctionality as revealed by NCO equivalent weight measurements. The NCOequivalent weight measurements were accomplished by reacting anyresidual NCO functionality in the sample with an excess amount ofdibutylamine. The amount of amine consumed (if any) can be thencalculated from titrating the amine with a standard acidic solution.

Example 6 Preparation of High Elongation Imparting Oligomer (5)

[0064] Into a two-liter, four-necked reaction kettle equipped with athermometer, a mechanical stirrer, and a condenser were charged 190.38parts of meta-tetramethylenexylyl diisocyanate, 327.62 parts ofisobornyl acrylate, 0.54 parts of dibutyltindilaurate, 1.51 parts of2,6-di-t-butyl-4-methylphenol, 0.21 parts of phenothiazine and 9.60parts of trimethylol propane. The mixture was heated to 65° C. and heldat that temperature for one hour. A sample was taken for isocyanate(“NCO”) equivalent weight measurement to confirm the completeness of thereaction. Thereafter, the mixture was cooled down to 35° C. and 32.42parts of hydroxyethyl acrylate were added dropwise to the reactor.Cooling was applied to the reactor during the addition as necessary tomaintain the reaction temperature below 40° C. The mixture was then heldat 38° C. for two hours. A sample was taken for NCO equivalent weightmeasurement to confirm the completeness of the reaction. Thereafter,1053.38 parts of polytetramethylene glycol with a number averagemolecular weight of 2000 (PolyTHF2000, BASF Corporation), 383.78 partsof phenoxyethyl acrylate, and 0.5 parts of dibutyltindilaurate wereadded to the reactor while controlling the temperature at around 65° C.The mixture was then held at 65° C. until it was significantly free ofisocyanate functionality as revealed by NCO equivalent weightmeasurements.

Example 7 Formulation (3)

[0065] The following ingredients were used to formulate a secondarycoating according to the present invention; 101.7 parts of oligomer (4)as synthesized above, 54.1 parts of oligomer (5) as synthesized above,17.6 parts of isobornyl acrylate (SARTOMER), 3.3 parts of phenoxyethylacrylate (SARTOMER), 23.5 parts of Photomer 8061 (COGNIS), 70.4 parts ofdi-trimethylolpropane tetra-acrylate (DiTMPTA) (SARTOMER), and 9.4 partsof Darocur 4265 (CIBA). The formulation had a viscosity of 4679 cps whenmeasured with a Brookfield viscometer at 25° C.

[0066] A five mil coating of this composition was applied to a flat,glass plate using a Bird applicator and cured at 1 J/cm² under a D-lampin a nitrogen atmosphere. The resulting free film gave a tensile stressat break of 40 MPa and an elongation of 10 percent when tested accordingto ASTM D-882. Dynamic mechanical analysis carried out at a frequency of1 Hz, speed of 2° C. per minute from −50° C. to 180° C. on the free filmgave a Tg of 100° C. and an equilibrium modulus of 34 MPa.

Example 8 Synthesizing of Lactone Modified Bisphenol A Epoxy Acrylate

[0067] Into a two-liter, four-necked reaction kettle equipped with athermometer, a mechanical stirrer and a condenser were charged 484.00parts of a bisphenol A epoxy diacrylate CN-104 (SARTOMER), 228.00 partsof E-caprolactone, and 2.00 parts of tin octoate. The mixture was heatedto 135° C. under a constant nitrogen blanket and was held at thattemperature for 6 hours. The reaction progress was monitored by samplingfor 110° C. solid measurements. The end point was reached when the 110°C. solid data is higher than 98 percent.

Synthesizing Oligomer from the Lactone Modified Bisphenol A EpoxyAcrylate (6)

[0068] Into a two-liter, four-necked reaction kettle equipped with athermometer, a mechanical stirrer, and a condenser were charged 37.0parts of meta-tetramethylenexylyl diisocyanate, 63.7 parts of isobornylacrylate, 0.3 parts of dibutyltindilaurate, 0.8 parts of2,6-di-t-butyl-4-methylphenol, 0.2 parts of phenothiazine and 1.9 partsof trimethylol propane. The mixture was heated to 80° C. and held atthat temperature for one hour. A sample was taken for isocyanate (“NCO”)equivalent weight measurement to confirm the completeness of thereaction. Thereafter, the mixture was cooled down to 35° C. and 6.3parts of hydroxyethyl acrylate were added dropwise to the reactor.Cooling was applied to the reactor during the addition as necessary tomaintain the reaction temperature below 40° C. The mixture was then heldat 38° C. for two hours. A sample was taken for NCO equivalent weightmeasurement to confirm the completeness of the reaction. Thereafter, ablend of 204.7 parts of polytetramethylene glycol with a number averagemolecular weight of 2000 (PolyTHF2000, BASF Corporation), 238.0 parts ofthe modified CN-104 as synthesized in Example 8, 341.1 parts ofphenoxyethyl acrylate, 185.0 parts of isopherone diisocyanate, and 0.3parts of dibutyltindilaurate was added to the reactor. The mixture washeated up to 80° C. slowly and held at that temperature for two hours. Asample was then taken for isocyanate (“NCO”) equivalent weightmeasurement to confirm the completeness of the reaction. Thereafter,116.0 parts of hydroxyethyl acrylate and 0.3 parts ofdibutyltindilaurate were added dropwise to the reactor. Cooling wasapplied to the reactor during the addition as necessary to maintain thereaction temperature at 80° C. The mixture was then held at 80° C. untilit was significantly free of isocyanate functionality as revealed by NCOequivalent weight measurements.

Synthesizing Oligomer from un-modified Bisphenol A Epoxy Acrylate (7)

[0069] Into a two-liter, four-necked reaction kettle equipped with athermometer, a mechanical stirrer, and a condenser were charged 37.0parts of meta-tetramethylenexylyl diisocyanate, 63.7 parts of isobornylacrylate, 0.3 parts of dibutyltindilaurate, 0.8 parts of2,6-di-t-butyl-4-methylphenol, 0.2 parts of phenothiazine and 1.9 partsof trimethylol propane. The mixture was heated to 80° C. and held atthat temperature for one hour. A sample was taken for isocyanate (“NCO”)equivalent weight measurement to confirm the completeness of thereaction. Thereafter, the mixture was cooled down to 35° C. and 6.3parts of hydroxyethyl acrylate were added dropwise to the reactor.Cooling was applied to the reactor during the addition as necessary tomaintain the reaction temperature below 40° C. The mixture was then heldat 38° C. for two hours. A sample was taken for NCO equivalent weightmeasurement to confirm the completeness of the reaction. Thereafter, ablend of 204.7 parts of polytetramethylene glycol with a number averagemolecular weight of 2000 (PolyTHF2000, BASF Corporation), 161.3 parts ofCN-104 (SARTOMER), 341.1 parts of phenoxyethyl acrylate, 185.0 parts ofisopherone diisocyanate, and 0.3 parts of dibutyltindilaurate was addedto the reactor. The mixture was heated up to 80° C. slowly and held atthat temperature for two hours. A sample was then taken for isocyanate(“NCO”) equivalent weight measurement to confirm the completeness of thereaction. Thereafter, 116.0 parts of hydroxyethyl acrylate and 0.3 partsof dibutyltindilaurate were added dropwise to the reactor. Cooling wasapplied to the reactor during the addition as necessary to maintain thereaction temperature at 80° C. The mixture was then held at 80° C. untilit was significantly free of isocyanate functionality as revealed by NCOequivalent weight measurements.

Formulations (4) and (5)

[0070] Two formulations were made according to the procedures asoutlined for formulation (3) above and the film properties were measuredunder the same conditions as used in formulation (3). The compositioninformation and film properties are included in the following table.TABLE 1 Comparative Formulation (4) Formulation (5) Composition Oligomer(6) 64.4 Oligomer (7) 66.8 Phenoxyethyl acrylate 4.4 2.0 (SARTOMER)DiTMPTA (SARTOMER) 24.0 24.0 Darocur 4265 (CIBA) 3.3 3.2 Formulationviscosity (cps) 4354 5042 Film Properties Tg (° C.) 72 82 EquilibriumModulus (MPa) 43 47 2.5% Secant Modulus (MPa) 1065 1200 Tensile (Mpa) 4144 Elongation (%) 20 10 Toughness (mJ/mm³) 7 4

[0071] As demonstrated in Table 1, use of a lactone modified epoxyresulted in increased elongation without significantly impacting otherparameters negatively.

[0072] Whereas particular embodiments of this invention have beendescribed above for purposes of illustration, it will be evident tothose skilled in the art that numerous variations of the details of thepresent invention may be made without departing from the invention asdefined in the appended claims.

What is claimed is:
 1. A composition comprising: a. a first radiationcurable urethane oligomer comprising at least three radiation curablefunctionalities; and b. a second radiation curable urethane oligomerdifferent from the first radiation curable urethane, wherein the firstradiation curable urethane oligomer comprises a lactone modified polyol.2. The composition of claim 1, wherein the polyol is adiphenylmethane-containing polyol.
 3. The composition of claim 1,wherein the first radiation curable urethane oligomer comprises two ormore aromatic rings.
 4. The composition of claim 1, wherein the lactonecomprises ε-caprolactone and/or derivatives thereof.
 5. The compositionof claim 1, wherein said composition has a Tg≧50° C. and an elongation≧15 percent.
 6. The composition of claim 1, wherein said secondradiation curable urethane oligomer comprises the reaction product oftetramethylxylene diisocyanate, a polyol having an Mn of greater than2000 daltons, and hydroxylethylacrylate.
 7. The composition of claim 6,wherein said polyol comprises polytetramethylene glycol andtrimethylolpropane.
 8. The composition of claim 1, further comprisingone or more reactive monomers.
 9. The composition of claim 8, wherein atleast one of the reactive monomers is monofunctional.
 10. Thecomposition of claim 1, wherein said first radiation curable urethaneoligomer comprises the reaction product of isophorone diisocyanate,lactone modified epoxy diacrylate, and 2-hydroxyethyl acrylate.
 11. Thecomposition of claim 1, wherein said first radiation curable urethaneoligomer has three radiation curable functionalities.
 12. Thecomposition of claim 1, wherein said first radiation curable urethaneoligomer has four radiation curable functionalities.
 13. A glass fibercoated with the composition of claim
 1. 14. An optical fiber ribbonarray containing a plurality of glass fibers bonded together in a matrixmaterial, wherein the matrix material is a cured composition of claim 1.15. The array of claim 14, wherein one or more of the glass fibers arealso coated with a composition comprising: a. a first radiation curableurethane oligomer comprising either three or four radiation curablefunctionalities; and b. a second radiation curable urethane oligomerdifferent from the first radiation curable urethane; wherein the firstradiation curable urethane oligomer comprises a lactone modified polyol.16. The glass fiber of claim 13, wherein the coating is a secondarycoating.
 17. A glass fiber comprising a secondary coating comprising: a.a first radiation curable urethane oligomer comprising at least threeradiation curable functionalities; and b. a second radiation curableurethane oligomer different from the first radiation curable urethane.